Deoxyribonucleic acid (DNA), sometimes called the “blueprint of life”, is a molecule that stores biological information. DNA has a basic structure that consists of two biopolymer strands, which are coiled around one another to form a double helix. Each strand is a polynucleotide that includes various nucleotides, which include cytosine (“C”), guanine (“G”), adenine (“A”), and thymine (“T”). Each nucleotide in one DNA strand may be bonded to a paired nucleotide in the other strand, thereby forming a base pair. Generally, cytosine and guanine are paired to form a “G-C” or “C-G” base pair, and adenine and thymine are paired to form an “A-T” or “T-A” base pair. Although the structure of DNA is now known, new methods to analyze individual DNA molecules are still being developed. Generally, the analysis includes “reading” the nucleotide sequence of a particular DNA strand. In one method, known as nanopore DNA sequencing, a nanopore is immersed in a conductive fluid, and a voltage is applied across the nanopore. As a result, ions are conducted through the nanopore, thereby generating a measurable electric current. A DNA strand is then transmitted through a nanopore, one nucleotide at a time. The presence of a nucleotide within the nanopore disrupts the conduction of the ions, thereby causing a change in the electric current. Moreover, the change in electrical current due to a particular nucleotide differs from the change in electrical current due to other nucleotides. Accordingly, an entire DNA strand can be transmitted through the nanopore and each nucleotide in the strand can be identified based on the change in current. Over time, the changes in electric current result in a DNA sensing signal reflecting the nucleotide sequence in a DNA strand.
As nanopore DNA sequencing improves, new challenges are presented. For example, although biological nanopores have shown promising experimental results to sequence single-stranded DNA (ssDNA), these protein pores have a constant pore size and lack stability. In addition, biological nanopores suffer from the fragility of traditional supported lipid membranes and a high membrane capacitance (˜50 femtofarads). The membrane capacitance may reduce the maximum cutoff frequency and thus limit the bandwidth associated with the DNA sensing signal in addition to increasing a noise component. As a result, new technologies are needed to further improve nanopore-based DNA sensing devices.